Shift control apparatus of automatic transmission and method therefor

Abstract

A shift control apparatus of an auto transmission of a vehicle and a method therefore, the method comprising steps of: discriminating whether a shift lever of an auto transmission is switched from reverse range `R` to neutral range `N`; calculating a lapse time when the shift lever is set at neutral range `N`, if it is confirmed that the shift lever is switched from reverse range `R` to neutral range `N` at the previous step and discriminating whether the shift lever is switched from neutral range `N` to forward drive range `D`; and performing a shifting operation with different shifting oil pressure depending on the lapse time, when the shift lever is set at the neutral range `N`, if it is confirmed that the shift lever is switched from neutral range `N` to the forward drive range `D` at the previous step, wherein the oil temperature of the automatic transmission of the running vehicle and the lapse time of the shift lever set at neutral range `N` are detected to differently control the shifting oil pressure, thereby reducing shift shock.

Description

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a shift control apparatus of an automatic transmission and a method therefor, and more particularly to a shift control apparatus of an automatic transmission and a method therefor to reduce shift shock that generates when a shift lever of an automatic transmission is switched from reverse range `R` to forward drive range `D` while a vehicle is at standstill.

[0003] 2. Brief Description of the Prior Art

[0004] In general automatic transmission of a vehicle, a shift control apparatus determines a target shift level according to all detected conditions such as running speed of a vehicle, openness of a throttle valve, and control oil pressure and performs shifting operations to the target shift stage.

[0005] In the automatic transmission thus constructed, the shifting operations to the target shift level involve fictional elements and changing from its operation released state to its operational state. A shift shock is generated depending on operational states of those frictional elements.

[0006] Accordingly, a variety of techniques have been developed and applied to reduce such shift shock. For instance, in order to reduce the shift shock at the beginning and end of shifting operations when the shift lever is switched from neutral range `N` to reverse range `R`, an accumulator is mounted onto a low/reverse brake, which is an operational element for an oil pressure circuit of an auto transmission to buffer the oil pressure that is supplied to the low/reverse brake.

[0007] However, the accumulator has the buffering operation of oil pressure that is supplied to the low/reverse brake, which means the accumulator has a slow shift response to release of oil pressure. If the shift lever of an auto transmission is directly switched from reverse range `R` to forward drive range `D`, an oil pressure of a servo-apply (S/A) is added, before oil pressure of the low/reverse brake is not completely released, to thereby result in the shift shock.

SUMMARY OF THE INVENTION

[0008] It is therefore an object of the present invention to solve the aforementioned problem and provide a shift control apparatus of an automatic transmission and a method therefor to reduce shift shock by detecting a lapse time of a shift lever set at neutral range `N`, when the shift lever is switched from reverse range `R` to forward drive range `D` and the oil temperature of the transmission and controlling the shifting oil pressure according to the detected values as such.

[0009] In order to accomplish the aforementioned object of the present invention, there is provided a shift control apparatus of an automatic transmission of a vehicle, the apparatus comprising:

[0010] vehicle operation detecting means for checking an operational state of a vehicle;

[0011] shift control means for calculating a lapse time of shift lever set at neutral range `N` when a shift lever is switched from reverse range `R` to neutral range `N` with an input of a signal detected by the vehicle operation detecting means and outputting a shift control duty signal to differently control the shift oil pressure according to the lapse time and the oil temperature detected by the vehicle operation means when the shift lever is switched from neutral range `N` to forward drive range `D`; and

[0012] drive means for performing shifting operations by providing a relevant frictional element with the oil pressure duty-controlled by a shift control duty signal output by the shift control means and discharged by an oil pump.

[0013] In order to accomplish the aforementioned object of the present invention, there is provided a shift control method of an auto transmission of a vehicle, the method comprising the steps of:

[0014] discriminating whether a shift lever of an auto transmission is switched from reverse range `R` to neutral range `N`;

[0015] calculating a lapse time when the shift lever is set at neutral range `N`, if it is confirmed that the shift lever is switched from reverse range `R` to neutral range `N` at the previous step, and discriminating whether the shift lever is switched from neutral range `N` to forward drive range `D`; and

[0016] performing shifting operations with different shifting oil pressure depending on the lapse time when the shift lever is set at the neutral range `N` if it is confirmed that the shift lever is switched from neutral range `N` to the forward drive range `D` at the previous step.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Objects and aspects of the invention will become apparent from the following description of a preferred embodiment with reference to the accompanying drawings in which:

[0018] FIG. 1 is a block view for illustrating the structure of a shift control apparatus of an automatic transmission of a vehicle in accordance with the present invention; and

[0019] FIG. 2 illustrates an operational sequence of a shift control method of an automatic transmission of a vehicle in accordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0020] A preferred embodiment of the present invention will be described with reference to accompanying drawings.

[0021] FIG. 1 is a block view for illustrating the structure of a shift control apparatus of an automatic transmission of a vehicle in accordance with the present invention, including: a vehicle operation detecting unit 100 for detecting the operational states of the vehicle variedly output according to an operational state of a vehicle; a shift control unit 200 for calculating a lapse time when a shift lever is set at neutral range `N` if it is confirmed that the shift lever is switched to neutral range `N` with an input of data such as openness of a throttle valve, revolutions of an output axle, engine rotations, oil temperature and position of the shift lever detected and output by the vehicle operation detecting unit 100 and outputting a predetermined shift control duty signal to perform shifting operations with different shifting oil pressure depending on the calculated lapse time of the shift lever at neutral range `N` and the oil temperature detected by the vehicle operation detecting unit 100; a drive unit 300 for performing shifting operations by providing a relevant frictional element with the oil pressure duty-controlled by a predetermined shift control duty signal output by the shift control unit 200 and discharged and supplied by an oil pump.

[0022] The vehicle operation detecting unit 100 is constructed with: a throttle valve openness detecting part 110 for detecting the openness of a throttle valve to be applied when a shift level is determined with the openness of the throttle valve communicating according to a driver's manipulation of an accelerator; an output axle revolution detecting part 120 for detecting revolutions of an output axle of an automatic transmission corresponding the running speed of the vehicle; an engine rotation detecting part 130 for detecting and outputting rotations of an engine; an oil temperature detecting part 140 for detecting and outputting the oil temperature of an automatic transmission; and a shift lever position detecting part 150 for checking whether the shift lever is set at reverse, neutral and forward drive ranges `R`, `N`, `D` depending on the driver's manipulation of the shift lever.

[0023] Now, shift control operations of an automatic transmission of a vehicle thus constructed will be described in detail with reference to FIG. 2.

[0024] As described above, the vehicle operation detecting unit 100 probes openness of a throttle valve, revolutions of an output axle, engine rotations, oil temperature and position of the shift lever.

[0025] Furthermore, the shift control unit 200 performs a shift control by a preset program with an input of openness of the throttle valve, revolutions of an output axle, engine rotations, oil temperature and position of a shift lever input from the vehicle operation detecting unit 100 to thereby run a vehicle. (S100)

[0026] In the middle of running of the aforementioned vehicle, the shift control unit 200 discriminates whether the shift lever is switched from reverse range `R` to neutral range `N`. (S110)

[0027] If it is confirmed that the shift lever is switched from reverse range `R` to neutral range `N` at step S110, the shift control unit 200 begins to calculate a lapse time (t) when the shift lever is set at neutral range (S120), and, then, discriminates whether the shift lever is switched from neutral range `N` to forward drive `D` by the driver. (S130)

[0028] Then, if it is confirmed that the shift lever is switched from neutral range `N` to forward drive range `D` by the driver, the shift control unit 200 discriminates whether the calculated lapse time (t) of the shift lever set at neutral range `N` is included within preset time range 1 of 0<t<100 ms. (S140)

[0029] If the lapse time (t) of the shift lever set at neutral range `N` is included within preset time range of 0<t<100 ms, the shift control unit 200 determines a duty value with reference to Table of an oil temperature map preset at memory as shown in Table 1 with an input of the oil temperature of an automatic transmission detected by the vehicle operation detecting unit 100 and outputs an initial PCSV. A duty control signal for the preset time with a duty value.

1TABLE 1 Oil T .ltoreq. 0.degree. C. 0.degree. C. .ltoreq. T .ltoreq. 30.degree. C. 30.degree. C. .ltoreq. T .ltoreq. 60.degree. C. 60.degree. C. .ltoreq. T .ltoreq. 100.degree. C. 100.degree. C. .ltoreq. T temperature T Duty value 50% 40% 30% 30% 30% (Dr)

[0030] However, if the lapse time (t), when the shift lever is set at neutral range `N`, calculated at step S140 is not included within time range 1 (0 ms<t<100 ms), the shift control unit 200 discriminates whether the lapse time (t), when the shift lever is set at neutral range `N`, calculated at step S120 is included within the preset time range 2 of 100 ms<t<1000 ms. (S200)

[0031] If it is confirmed that the previously calculated lapse time (t), when the shift lever is set at neutral range `N`, is included within the preset time range 2 of 100 ms<t<1000 ms, the shift control unit 200 outputs the preset initial PCSV-A duty control signal to the drive unit 300 for a predetermined time. (S210)

[0032] The drive unit 300 is duty-controlled by a duty control signal output by the shift control unit 200 to control oil pressure to perform shifting operations from the current range to a driver's desired range, thereby completing shifting operations.

[0033] When the shift lever is switched by the driver's manipulation to neutral range `N` and forward drive range `D` while the vehicle is driven at reverse range `R`, a shift control duty signal is differently output depending on the oil temperature of the running vehicle and the lapse time of the shift lever set at neutral range `N`. Therefore, it is possible to differently control the oil pressure of the drive unit 300, so that the shifting operations can be performed without any shift shock even when the shift lever is switched.

[0034] As described above, there are advantages in the shift control apparatus of the automatic transmission and its method in accordance with the present invention in that the oil temperature of the automatic transmission of the running vehicle and a lapse time of the shift lever set at neutral range `N` are detected to differently control the shifting oil pressure, thereby reducing a shift shock and improving a shifting function and convenience of the automatic transmission.

Claims

What is claimed is:

1. A shift control apparatus of an automatic transmission of a vehicle, the apparatus comprising: vehicle operation detecting means for checking an operational state of a vehicle; shift control means for calculating a lapse time of shift lever set at neutral range `N` when a shift lever is switched from reverse range `R` to neutral range `N` with an input of a signal detected by the vehicle operation detecting means and outputting a shift control duty signal to differently control the shift oil pressure lo according to the lapse time and the oil temperature detected by the vehicle operation means when the shift lever is switched from neutral range `N` to forward drive range `D`; and drive means for performing shifting operations by providing a relevant frictional element with the oil pressure duty-controlled by a shift control duty signal output by the shift control means and discharged by an oil pump.

2. The apparatus, as defined in claim 1, wherein the vehicle operation detecting means comprises: a throttle valve openness detecting part for detecting the openness of a throttle valve to be applied when a shift level is determined with the openness of the throttle valve communicating according to a driver's manipulation of an accelerator; an output axle revolution detecting part for detecting revolutions of an output axle of an automatic transmission corresponding to the running speed of the vehicle; an engine rotation detecting part for detecting and outputting rotations of an engine; an oil temperature detecting part for detecting and outputting the oil temperature of an automatic transmission; and a shift lever position detecting part for checking whether the shift lever is set at reverse, neutral and forward drive ranges `R`, `N`, `D`depending on the driver's manipulation of the shift lever.

3. A shift control method of an auto transmission of a vehicle, the method comprising the steps of: discriminating whether a shift lever of an auto transmission is switched from reverse range `R` to neutral range `N`; calculating a lapse time when the shift lever is set at neutral range `N`, if it is confirmed that the shift lever is switched from reverse range `R` to neutral range `N` at the previous step and discriminating whether the shift lever is switched from neutral range `N` to forward drive range `D`; and performing a shifting operation with different shifting oil pressure depending on the lapse time when the shift lever is set at the neutral range `N` if it is confirmed that the shift lever is switched from neutral range `N` to the forward drive range `D` at the previous step.

4. The method, as defined in claim 3, wherein the shifting step further comprises the steps of: discriminating whether the lapse time, when the shift lever is set at neutral range, is included within preset time range 1; and setting a shift control duty value on basis of the oil temperature of an automatic transmission and Table of the oil temperature map preset at memory and outputting a relevant duty control signal for a predetermined time if it is confirmed that the calculated lapse time of the shift lever set at neutral range `N` is included within the time range 1.

5. The method, as defined in claim 4, wherein the time range 1 is 0 ms<the lapse time of the shift lever set at neutral range `N`<100 ms.

6. The method, as defined in claim 3, wherein the shifting step further comprises the steps of: discriminating whether the lapse time, when the shift lever is set at neutral range, is included within preset time range 2 after it is confirmed that the calculated lapse time, when the shift lever is set at neutral range `N`, is not within the time range 1; and setting a shift control duty value preset at memory and outputting a relevant duty control signal for a predetermined time if it is confirmed that the lapse time of the shift lever set at neutral range `N` is included within time range 2 at the previous step.

7. The method, as defined in claim 6, wherein the time range 2 is 100 ms<the lapse time of the shift lever set at neutral range `N`<1000 ms.